1. Field of the Invention
This invention relates generally to tape cassettes, and more particularly is directed to improvements in magnetic tape cassettes provided with reel brake assemblies which are engaged or operative when the cassette is not in use.
2. Description of the Prior Art
Recently, it has been proposed to provide an improved cassette recording and/or reproducing apparatus in which a magnetic tape extending between supply and takeup reels contained in a cassette housing may be withdrawn from the housing for the high quality recording and reproducing of information signals on the tape. Generally, the tape cassette provided for use in such an apparatus has a relatively large opening in the peripheral wall of the cassette housing to permit the magnetic tape to be withdrawn therethrough. Therefore, if the magnetic tape is loosened, as by turning of one or both of the reels in the direction for unwinding the tape therefrom while the cassette is not in use, there is the danger that the loosened tape may inadvertently exit from the housing through the large opening of the latter and thus be susceptible to being damaged or even severed. Even if the loosened tape does not exit from the cassette housing, it is possible that the loosened tape within the housing will not be positioned so as to make possible its controlled withdrawal from the cassette housing when the cassette is subsequently installed on the recording and/or reproducing apparatus.
Various tape cassettes have been proposed in which braking means are provided within the cassette housing to resist unwinding or loosening of the tape when the cassette is not in use. In some of these known tape cassettes, for example, as disclosed in U.S. Pat. No. 3,027,111, a braking member having serrated, converging side edges is movable longitudinally between the supply and takeup reels and is urged by a spring to move in the direction in which such side edges converge so as to engage the serrated side edges with the wheel hubs. A projection extends longitudinally from the braking member and is exposed at an opening of the cassette housing so as to be actuable for moving the braking member in the opposite longitudinal direction and thereby freeing the reels for rotation when the cassette is installed in a recording and/or reproducing apparatus. The foregoing tape cassette is disadvantageous in that, when the cassette is removed from the recording and/or reproducing apparatus to permit the spring to return the braking member longitudinally to its engaged position, the serrated edges of the braking member act, in the course of such return movement, to impart incremental rotary movements to the reels in the tape-unwinding direction with the result that the tape extending between the reels is loosened to some extent. Further, if loosening of the tape has occurred, the manual rotation of a reel in the direction for rewinding the tape thereon and removing the slack from the tape has to be effected against the relatively large frictional resistance of the engaged braking member under the urging of the spring acting thereon.
In another similar proposed tape cassette provided with braking means, for example, as specifically disclosed in U.S. Pat. No. 3,800,322, supply and takeup reels on which the tape is wound are rotatably mounted in side-by-side relation within the cassette housing, and such reels are provided with inclined serrations in the peripheries of their flanges. A wedge-shaped locking or brake member formed with serrations on the opposite sides thereof is situated between the flanges of the reels and is urged by a spring to move in the direction for engaging the serrations of the locking or brake member with the serrated peripheries of the reel flanges, whereby to hold the reels against rotation in the direction for unwinding the tape therefrom. When such tape cassette is installed in a recording and/or reproducing apparatus, an actuating pin or member of such apparatus enters the cassette housing and acts on the wedge-shaped locking or brake member so as to displace the latter against the spring force, that is, in the direction for removing the serrated side edges of the locking or brake member from the serrated peripheries of the reel flanges, whereupon the reels are free to be rotated. When the tape cassette is removed from the recording and/or reproducing apparatus, the locking or brake member is returned to its operative or engaged position by the associated spring, and such return movement again imparts rotary movements to the reels in the tape-unwinding direction so that the tape is loosened. If the serrations provided on the reel flanges and on the wedge-shaped locking or brake member are suitably inclined, the reels may be manually turned in the direction to rewind the tape thereon even when the locking or brake member is in its engaged position but such turning of the reels has to be effected against the resistance of the spring acting on the wedge-shaped locking or brake member, and such spring desirably exerts a substantial force in order to ensure the retention of the locking or brake member in its engaged position when the cassette is not in use.
In still another proposed braking means associated with an endless tape cartridge, for example, as specifically disclosed in U.S. Pat. No. 3,637,152, a flange of the reel is formed with serrations that are inclined to the radii of the reel, and a locking lever pivotally mounted intermediate its ends within the cartridge housing is formed with a hooked end and is spring urged to pivot in the direction moving the hooked end against the serrated periphery of the reel flange. The opposite end of the locking lever is pivotally connected to an actuating slide which is exposed at an opening of the cartridge housing. When the cartridge is inserted in a reproducing or playback apparatus, the magnetic head of such apparatus displaces the actuating slide so as to pivot the locking lever in the direction moving its hooked end away from the serrated periphery of the reel flange so as to free the reel for rotation. Upon the removal of the cartridge from the playback apparatus, the spring acting on the locking lever returns the latter to its operative position in which the hook engages in an inclined serration of the reel flange for locking the latter against rotation in one direction. Although the inclination of the serrations permits the reel to be manually turned in the opposite direction even when the cartridge is not in use, it will be apparent that such turning of the reel is relatively strongly resisted by the appreciable spring force acting on the locking lever to ensure its return movement to the operative position thereof when the cassette is removed from the playback apparatus.